锗对水稻的生态毒理效应及临界指标

Eco-toxicological effects of germanium stress on rice(Oryza sativa L.) and their critical value

土壤添加 Ge盆栽试验研究表明 ,低浓度 Ge(<4 m g/ kg)对水稻根和地上生物量、叶绿素 a含量有促进作用 ,并整体提高了作物抗氧化酶能力 ,使 MDA下降 ,SOD、CAT、POD、GSH- Px活性相应提高。而高浓度 Ge(>15 mg/ kg)对水稻根和地上生物量、叶绿素 a含量有明显的抑制作用 ,对抗氧化酶系统产生胁迫效应 ,使 POD明显上升 ,MDA上升 ,SOD、CAT酶活性明显下降。在高浓度 Ge胁迫下 ,植物细胞中抗氧化作用酶系统的受损打破了植物细胞内活性氧产生与清除间的正常平衡状态 ,积累过量的活性氧 ,使活性氧产生并积累 ,过量的活性氧引起膜脂过氧化程度加重 ,从而对植物产生毒害。各项生理指标与土壤 Ge处理浓度之间相关分析表明 ,土壤 Ge浓度与地上部干重相对百分率 ,根干重百分率、叶绿素 a/ b、MDA、SOD、CAT之间有显著相关性。比较胁迫效应 10 %值的临界指标 EC1 0 值表明 ,作物地上部干重抑制率和根干重抑制率作为土壤临界值制定的依据更为可靠 ,EC1 0 为 7m g/

Germanium (Ge), a Ⅳb group element, exists in soil, rocks, animals, and plants in many organic or inorganic forms. While germanium dioxide (GeO_2) is the main natural inorganic type, the organic type has three subtypes. The application of both inorganic and organic germanium is increasing in recent years. Germanium has gradually replaced silicon in modern electronic industry, especially in integrated circuit (IC) manufacturing; germanium tetrachloride (GeCl_4) is employed in making the optical fibres for high speed (digital corresponding) transmission of digital data. Germanium compounds are discharged to the environment with solid wastes from the electronic industry causing potential risks to ecosystem in different levels, i.e., individual, population, community and ecosystem. Their fate and potential impacts are so far still unknown. The aim of this study was to determine the eco-toxicology effects of Ge on the growth and scavenging system of activated oxygen of rice (Oryza sativa L.). Soil cultures were employed to study the physiological and ecological responses of rice. Nine concentration levels of Ge (0,2,4,8,12, 15,30,50,100mg/kg) were used in the yellow-brown soil experiments. The test results showed that a low level of Ge(<4 mg/kg)added to soil enhanced rice biomass, chlorophyll a, and antioxidative enzymes activities and increased SOD, CAT,POD, GSH-Px activity, while decreased MDA content. The results also showed a high level of Ge (>15mg/kg) added to soil inhibited the biomass, chlorophyll a and had a stress effect on antioxidative enzyme system resulting in significantly increased POD activity, increased MDA content, and, at the same time, significantly decreased SOD and CAT. These results indicated that, under the stress of a high Ge level, the decline of antioxidative enzyme activities broke the normal balance between production and elimination of active oxygen, resulting in the accumulation of excessive active oxygen which aggravated lipid peroxidation and thereby caused toxic effects on rice. In pot experiments, the concentration of Ge in soil showed significant correlation to the physiological indexes (roots biomass, shoots biomass, chlorophyll a/b,MDA, SOD, CAT). The 10 % inhibition rate of shoots biomass, or EC_(10), was found to be a good indicator of the critical value for Ge in soil. For this study, EC_(10) was 7 mg/kg.